ICT Network Project

The main Icinga configuration file is /etc/icinga/icinga.cfg , additional configurations are stored in /etc/icinga/commands.cfg and /etc/icinga/resource.cfg . Usually the default configuration is ok, so you don't have to change these files.

The first thing you should change is the contact details in /etc/icinga/objects/contacts_icinga.cfg so that notifications are sent to the correct email address:

vi /etc/icinga/objects/contacts_icinga.cfg

[...]
define contact{
   contact_name                    root
        alias                           Falko Timme
        service_notification_period     24x7
        host_notification_period        24x7
        service_notification_options    w,u,c,r
        host_notification_options       d,r
        service_notification_commands   notify-service-by-email
        host_notification_commands      notify-host-by-email
        email                           me@myself.com
        }
[...]

The service checks for localhost are defined in /etc/icinga/objects/localhost_icinga.cfg - take a look at that file:

cat /etc/icinga/objects/localhost_icinga.cfg

# A simple configuration file for monitoring the local host
# This can serve as an example for configuring other servers;
# Custom services specific to this host are added here, but services
# defined in icinga-common_services.cfg may also apply.
#

define host{
        use                     generic-host            ; Name of host template to use
        host_name               localhost
        alias                   localhost
        address                 127.0.0.1
        }

# Define a service to check the disk space of the root partition
# on the local machine.  Warning if <20% free, critical if
# <10% free space on partition.

define service{
        use                             generic-service         ; Name of service template to use
        host_name                       localhost
        service_description             Disk Space
        check_command                   check_all_disks!20%!10%
        }

# Define a service to check the number of currently logged in
# users on the local machine.  Warning if> 20 users, critical
# if> 50 users.

define service{
        use                             generic-service         ; Name of service template to use
        host_name                       localhost
        service_description             Current Users
        check_command                   check_users!20!50
        }

# Define a service to check the number of currently running procs
# on the local machine.  Warning if> 250 processes, critical if
#> 400 processes.

define service{
        use                             generic-service         ; Name of service template to use
        host_name                       localhost
        service_description             Total Processes
                check_command                   check_procs!250!400
        }

# Define a service to check the load on the local machine.

define service{
        use                             generic-service         ; Name of service template to use
        host_name                       localhost
        service_description             Current Load
                check_command                   check_load!5.0!4.0!3.0!10.0!6.0!4.0

  }

Let's check out the /etc/nagios-plugins/config/disk.cfg file:

cat /etc/nagios-plugins/config/disk.cfg

# 'check_disk' command definition
define command{
   command_name    check_disk
        command_line    /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e -p '$ARG3$'
        }

# 'check_all_disks' command definition
define command{
        command_name    check_all_disks
        command_line    /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e
        }

# 'ssh_disk' command definition
define command{
        command_name    ssh_disk
        command_line    /usr/lib/nagios/plugins/check_by_ssh -H '$HOSTADDRESS$' -C __GESHI_QUOT__          /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e -p '$ARG3$'__GESHI_QUOT__
        }

####
# use these c

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hecks, if you want to test IPv4 connectivity on IPv6 enabled systems
####

# 'ssh_disk_4' command definition
define command{
        command_name    ssh_disk_4
        command_line    /usr/lib/nagios/plugins/check_by_ssh -H '$HOSTADDRESS$' -C "       /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e -p '$ARG3$'"        -4
        }

As you see, the check_all_disks command is defined as /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e . If you take a look at the /etc/icinga/objects/localhost_icinga.cfg file again, you see that we have the line check_command check_all_disks!20%!10% in it. Icinga allows us to pass command line arguments to service checks by separating them with an exclamation mark ( ! ), so check_command check_all_disks!20%!10% means we pass 20% as the first command line argument and 10% as the second command line argument to the /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e command so that it finally translates to /usr/lib/nagios/plugins/check_disk -w '20%' -c '10%' -e.

If you want to pass a command line argument that contains an exclamation mark, you must escape the exclamation mark with a backslash: \!

To find out what command line arguments a plugin can take, call that plugin with the –help switch. For example, to find out how the check_disk plugin can be used, run

/usr/lib/nagios/plugins/check_disk --help

With this knowledge you can modify the service checks in /etc/icinga/objects/localhost_icinga.cfg to your likings, and you can add/modify plugin configurations in the /etc/nagios-plugins/config directory.

Now let's assume we want to add a service check for MySQL, we first take a look at the appropriate plugin configuration:

cat /etc/nagios-plugins/config/mysql.cfg

# 'check_mysql' command definition
define command{
        command_name    check_mysql
        command_line    /usr/lib/nagios/plugins/check_mysql -H '$HOSTADDRESS$'
}

# 'check_mysql_cmdlinecred' command definition
define command{
        command_name    check_mysql_cmdlinecred
        command_line    /usr/lib/nagios/plugins/check_mysql -H '$HOSTADDRESS$' -u '$ARG1$' -p '$ARG2$'
}

# 'check_mysql_database' command definition
define command{
        command_name    check_mysql_database
        command_line    /usr/lib/nagios/plugins/check_mysql -d '$ARG3$' -H '$HOSTADDRESS$' -u '$ARG1$' -p '$ARG2$'
}

The command I want to use is check_mysql_cmdlinecred - this takes a MySQL username and a password as arguments (besides the host address which is taken from the host_name parameter of the service check definition. I want to use the MySQL user nagios with the password howtoforge here, so I add the following section to /etc/icinga/objects/localhost_icinga.cfg :

vi /etc/icinga/objects/localhost_icinga.cfg

[...]
define service{
       use                             generic-service
       host_name                       localhost
       service_description             MySQL
       check_command                   check_mysql_cmdlinecred!nagios!howtoforge
}

Before we restart Icinga, we must create the MySQL user nagios with the password howtoforge :

mysql -u root -p

GRANT USAGE ON *.* TO nagios@localhost IDENTIFIED BY 'howtoforge';
GRANT USAGE ON *.* TO nagios@localhost.localdomain IDENTIFIED BY 'howtoforge';
FLUSH PRIVILEGES;

quit;

(The USAGE privilege is a synonym for 'no privileges', i.e., the nagios user can connect to MySQL, but not alter or read any data.)

Now we restart Icinga so that our changes take effect:

/etc/init.d/icinga restart

If you check localhost 's services in the Icinga web interface now, you should see that a check for MySQL has been added:

http://static.howtoforge.com/images/icinga_monitoring_ubuntu_11.10/big/4.pngLikewise, we can add checks for SMTP, POP3, and IMAP - these are just connection checks, so we don't need any arguments:

vi /etc/icinga/objects/localhost_icinga.cfg

[...]
define service{
       use                             generic-service
       host_name                       localhost
       service_description             SMTP
       check_command                   check_smtp
}
define service{
       use                             generic-service
       host_name                       localhost
       service_description             POP3
       check_command                   check_pop
}
define service{
       use                             generic-service
       host_name                       localhost
       service_description             IMAP
       check_command                   check_imap
}

Restart Icinga…

/etc/init.d/icinga restart

… and a few moments later you should see the new checks in the Icinga web interface:

http://static.howtoforge.com/images/icinga_monitoring_ubuntu_11.10/big/5.pngYou might have noticed the SSH and HTTP checks for localhost which are not defined in /etc/icinga/objects/localhost_icinga.cfg . These are defined in hostgroup s in the /etc/icinga/objects/hostgroups_icinga.cfg file. A hostgroup allows us to run a service check for multiple servers and define it only once. Take a look at that file:

cat /etc/icinga/objects/hostgroups_icinga.cfg

# Some generic hostgroup definitions

# A simple wildcard hostgroup
define hostgroup {
        hostgroup_name  all
                alias           All Servers
                members         *
        }

# A list of your Debian GNU/Linux servers
define hostgroup {
        hostgroup_name  debian-servers
                alias           Debian GNU/Linux Servers
                members         localhost
        }

# A list of your web servers
define hostgroup {
        hostgroup_name  http-servers
                alias           HTTP servers
                members         localhost
        }

# A list of your ssh-accessible servers
define hostgroup {
        hostgroup_name  ssh-servers
                alias           SSH servers
                members         localhost
        }

As you see, we have a hostgroup called http-servers and a hostgroup called ssh-servers , and localhost is a member of each of these groups. The service checks for the hostgroup s are defined in /etc/icinga/objects/services_icinga.cfg . This file contains service checks and refers to the hostgroup s to which these checks should be applied by using the hostgroup_name parameter:

cat /etc/icinga/objects/services_icinga.cfg

# check that web services are running
define service {
        hostgroup_name                  http-servers
        service_description             HTTP
        check_command                   check_http
        use                             generic-service
        notification_interval           0 ; set> 0 if you want to be renotified
}

# check that ssh services are running
define service {
        hostgroup_name                  ssh-servers
        service_description             SSH
        check_command                   check_ssh
        use                             generic-service
        notification_interval           0 ; set> 0 if you want to be renotified
}

As you see, the SSH and HTTP service checks are defined here.